Percutaneous coronary intervention (PCI) is a procedure for treating heart disease. A catheter assembly having a balloon portion is introduced percutaneously into the cardiovascular system of a patient via the brachial or femoral artery. The catheter assembly is advanced through the coronary vasculature until the balloon portion is positioned across the occlusive lesion. Once in position across the lesion, the balloon is inflated to a predetermined size to radially compress the atherosclerotic plaque of the lesion to remodel the lumen wall. The balloon is then deflated to a smaller profile to allow the catheter to be withdrawn from the patient's vasculature.
Problems associated with the above procedure include formation of intimal flaps or torn arterial linings which can collapse and occlude the blood conduit after the balloon is deflated. Moreover, thrombosis and restenosis of the artery may develop over several months after the procedure, which may require another angioplasty procedure or a surgical by-pass operation. To reduce the partial or total occlusion of the artery by the collapse of the arterial lining and to reduce the chance of thrombosis or restenosis, a stent is implanted in the artery to keep the artery open. Such a stent can be a biodegradable stent.
Most biodegradable stent designs require high radial strength and are therefore prepared from highly crystalline polymers such as poly(L-lactic acid) (PLLA). Recently discoveries suggest that self-expandable stent designs may be better for therapeutic indications such as vulnerable plaque where lower radial strength is required. For these biodegradable stent designs it is important to have mechanical integrity and good shelf life stability.
The embodiments of the present invention address the above-identified needs and issues.